Belt Driven Generator Frequently Asked Questions

  • Can I operate the AB25, AB50, AB60, AR100 and AR250 in both clockwise or counter clockwise directions when facing the extended shaft?
            Yes.  All models can be operated either clockwise or counter clockwise.
  • What are the shaft diameters?
            The models AB25, AB50 and AB60 have an outside diameter of .875 inches (7/8") with a .1875 (3/16") keyway.  The    key is included.  Model AR100 has an outside diameter of 1.0 inch with a .25 inch (1/4") keyway.  The key is included.  The AR250 has an outside diameter of 35MM (1.377")  with a 10MM (13/32") keyway. The key is included.
  • What size pulley do I need to operate the generator?
            See the web page  Determining Pulley Diameter.  Please note that models AB25, AB50 and AB60 require a single pulley with preferably a "B" size belt.  Model AR100 MUST us a two groove "B" pulley and AR250 requires a three groove pulley.
  • Where can I buy a pulley?
            Local automotive supply companies, industrial supply companies, W.W. Granger, King Bearing, Motion Industries, etc.
  • What size engine do I need to operate the generator?
            AB25 requires 5 H.P.
            AB50 requires 8 H.P.
            AB60 requires 11 H.P.
            AR100 requires 16 to 18 H.P.
            AR250 requires 50 H.P.
            Practically all one and two cylinder engines (Briggs and Stratton, Vanguard, Honda, Kohler, Onan, Robin, Kawasaki, Kubota, Tecumseh, etc.) have rated horse power only when operating at 3600 R.P.M.  If you operate these types of engines below 3600 R.P.M., you will reduce the horse power of these engines.  Also, if you use a garden tractor engine they are usually governed down in speed and possibly only 2/3 of the rated horse power will be available.  If automobile engines are used, even though the rated horse power is substantially above 18 horse power, if the engine is only idling, you may not have enough horse power.  Engines have power curves and idling speed allows very small amounts of available horse power.  You must operate automobile engines at enough speed to have sufficient horse power.  All engines MUST have a mechanical governor to fix the speed of the engine.
  • What will happen if I do not have enough horse power to run the generator?
            All of the above generators require the horse power listed to obtain the rated electrical output.  If you do not have enough horse power, you will not get the full power out of the generator.  If you try to get the rated output (wattage) and do not have enough horse power, you will get low voltage and higher amperage which can cause damage to the items you are operating and cause damage to the generator.
  • If I do not have enough horse power, won't the circuit breakers trip and protect the circuit by preventing high amperage form damaging the items that the generator is operating?
            All of the circuit breakers ar thermal types which can hold up to 25% overload.  These circuit breakers can take a while to heat up before tripping to protect a circuit.  During the time the circuit breakers is heating up, the high amperage is potentially causing damage to the items the generator is operating.  If there is a dead short circuit, the circuit breakers will immediately trip.
  • Instead of using pulleys, can I directly couple the generator to an engine?
            Yes.  In order to directly couple these generators to an extended shaft engine, you must use couplings with spider gears.  These types of couplings are available from companies such as Lovejoy or Boston Gear and are available at most industrial supply companies such as WW Grainger etc.  One coupling must fit the diameter of the generator shaft and one coupling must fit the diameter of the engine shaft.  The spider insert fits between the two couplings to compensate for misalignment.
  • If I do not need a lot of power from the generator, can I operate the generator at slow speeds?
            No!  All models of two bearing generators MUST operate at 3600 R.P.M.  If the generator speed os less than 3600 R.P.M., the voltage and frequency (hertz) will be lower than required and if the generator operates above 3600 R.P.M., the voltage and frequency (hertz) will be higher than required.  Either condition will cause damage to the items being operated by the generator and also to the generator.  Generator shaft speed below 3400 R.P.M. and above 3800 R.P.M. will cause damage to items and the generator.
  • How do I know what speed the engine and generator are running?
            All Voltmaster generators have a voltmeter (except model AB25-PW).  It is recommended that you use a tachometer to determine the shaft speed  of the generator (3600 R.P.M.).  If a tachometer is not available, when the voltmeter reads at least 240 volts (except AB25 which reads 120 volts to a maximum of 130 volts) to a maximum of approximately 250 volts, you have reached 3600 R.P.M. on the generator shaft.  For model AB25-PW you need to plug in a voltmeter into the 120 volt receptacle and upon reaching 125 to 130 volts, you are at the proper generator shaft speed.
  • I have a tractor.  Can I run these generators off the power take off (PTO)?
            No.  The PTO's on tractors operate at either 540 R.P.M. on small horse power tractors (usually below 40 horse power) or 1000 R.P.M. on larger tractors.  All of these generators MUST operate at 3600 R.P.M.  and a direct coupling to the tractors will cause low voltage.  We do offer tractor driven PTO generators.
  • I have a garden tractor and want to operate the generator in the vertical  mode.  Can this be done?
            No.  All of these generators are designed to operate in the horizontal mode.  The generators will operate vertically, however they all have ball bearings and vertical operation should require tapered roller bearings.  There is NO warranty for operation in the vertical mode.
  • I just received my generator and I can not get any electrical output from the unit.  What is wrong?
            Assuming the shaft of the generator rotates freely, the most common problem is lack of enough speed being transmitted from the engine to the generator.  All of these generators do not start producing electricity until they reach a minimum speed of at least 2200 to 2400 R.P.M.  Even at those low speeds, the voltage on the generator is only operating at about 50%.  Correct operating voltages of 120 and 240 volts will NOT occur until the generator shaft runs at 3600 R.P.M..
  • Can I use a hydraulic motor to run a generator?
            Yes as long as you adjust the speed of the hydraulic motor to rotate the generator shaft at 3600 R.P.M..
  • What is the warranty on these units?
            There is a one year limited parts and labor warranty on all two bearing generators.
  • The owners manual indicates a belt guard must be installed.  Why wasn't one provided with the generator?
            The generator manufacturer has no idea of what size engine, pulleys or coupling will be used and therefore a belt guard was not provided.
  • Why wasn't a pulley provided with the generator?
            The generator manufacturer has no idea of what size or type of engine the end user of the generator has.
  • Can I run a computer, sound system or other electronic equipment on these generators?
            Models AB25, AB50, AB60, AR100 and AR250 all feature voltage regulation +-5% and distortion of 6% or less.  The end user's engine and governor determines the ultimate output of the generator.  If the engine governor is +-5%, it is safe to operate electronic equipment.  It is always strongly recommended to use a U.P.S. (battery) system on all computers.   If the generator is operating electronic equipment and electronic motors ( sump pumps, refrigerators, fans, pumps, garage doors, compressors, etc.) these devices require the engine governor to increase or decrease significantly and the engine speed will change the electrical output and increase or decrease voltage and frequency.  Caution must be used when operating electronic equipment and electric motors at the same time.

The rotor, stator, and other electrical components are covered by a 1 year limited warranty against defects in material and workmanship from date of purchase.  The 1 year limited warranty on the engine is covered separately by the engine manufacturer.

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